The present invention relates to a device for providing a seal between a shaft and a housing. In particular, the present invention relates to a static and dynamic seal device for preventing lubricant from leaking out of a housing and/or for preventing contaminants from traveling into the housing.
Prior art devices for sealing a rotating shaft are disclosed in U.S. Pat. No. 4,022,479 (Orlowski) and U.S. Pat. No. 5,024,451 (Borowski). Seal devices of this type may be used to prevent lubricant from escaping out of a bearing housing and/or to prevent contaminants from working their way into the housing. The prior art devices are formed of at least two ring-shaped members that rotate with respect to each other when the shaft is rotated. One of the members is fixed to the housing and does not rotate. The other member rotates with the rotating shaft.
The two ring members should be located very close together, particularly when the seal device is used to isolate the bearing from small particulate contaminants. Even small quantities of such contaminants are capable of significantly deteriorating the bearing. To prevent such contamination, the two relatively rotatable ring members must be held together very closely, with only a very narrow space therebetween.
The ring members of the Orlowski seal device are connected together by a separate securing means, not shown in the prior art patent. The ring members themselves have no means for establishing and maintaining a narrow spacing therebetween. Therefore, the prior art seal device cannot be manufactured as a unit with a preset, fixed spacing. The spacing between the ring members has to be set when the seal device is installed into the housing. This leaves room for human error outside the control of the device manufacturer. In particular, the Orlowski device can be improperly installed, with the ring members located too far apart to perform satisfactorily. Another problem with the Orlowski device is that the ring members may be separated subsequent to installation, for example by high pressure cleaning spray.
The ring members of the Borowski device are held together by a bead and a groove provided on the ring members themselves. The bead fits within the groove with an interference fit. This arrangement is an improvement over the Orlowski system in the sense that no separate securing means is needed. But the Borowski device is still unsatisfactory because the bead must be resiliently deformed to be positioned within the groove, and the groove must be correspondingly enlarged to receive the deformed bead. The deformation of the bead during assembly makes it difficult to achieve the desired close positioning between the two ring members, as explained in more detail below.
Furthermore, neither the Orlowski system nor the Borowski device provide satisfactory static sealing in flooded conditions as well as dynamic sealing during operation.
Prior art devices showing labyrinth and/or contact seals are disclosed in U.S. Pat. No. 5,259,628 (Nisley), U.S. Pat. No. 5,028,054 (Peach), and U.S. Pat. No. 4,379,600 (Muller). The device referred to in Muller is a dust seal between an inner race and an outer race. The dust seal is accomplished either through a labyrinth arrangement of L-shaped rings or through a contact seal. The device of Muller provides no mechanism for sealing, either dynamically or statically, fluid from exiting the device.
The device disclosed by Nisley is a seal assembly with a rotor, a housing, a V-ring and a metal ring. The housing and the rotor have alternating teeth and grooves which intermesh to form a labyrinth seal. The metal ring fits within an angular groove in the housing. The V-ring is positioned on the rotor and makes contact with the metal ring. The device as disclosed by Nisley is, thus, formed of four separate machined pieces, and is relatively expensive to manufacture. Such a seal device, since it has four separate parts which must be fit together, will have correspondingly greater leakage points than a seal device with fewer parts. Further, the V-ring is positioned to make contact with a metal ring, which may wear the V-ring, leading to an opening between the housing and the rotor through which contaminants and fluid may travel.
The device referred to in Peach has, like Nisley, numerous separately machined or formed parts, thus increasing the device's expense, complexity and possibility of leakage.